New determination of the adiabatic ionization potential of the BaOH radical from laser photoionization-molecular beam experiments and ab initio calculations

Abstract

The adiabatic ionization potential of the BaOH radical, as generated in a laser vaporization-supersonic expansion source has been determined by laser photoionization experiments to be (4.55 ± 0.03) eV. This value supports the three lowest out of seven previous experimental estimates, the former ranging from 4.35 to 4.62 eV. The present result is compared to ab initio calculations, as performed using both quantum chemistry at different levels of theory and density functional theory, and trying several effective core potentials and their accompanying basis sets for Ba. The most satisfactory agreement is obtained for either the adiabatic or vertical ionization potentials that derive from post-Hartree-Fock [MP2 and CCSD(T)] treatments of electron correlation, along with consideration of relativistic effects and extensive basis sets for Ba, in both BaOH and BaOH(+). Such conclusions extend to the results of related calculations on the Ba-OH dissociation energies of BaOH and BaOH(+), which were performed to help in calibrating the present computational study. Bonding in BaOH/BaOH(+), as well as possible sources of discrepancy with previous experimental determinations of the BaOH adiabatic ionization potential are discussed.

Solvation of barium atoms and singly charged cations in acetonitrile clusters

“…The dominant BaNC + mass peak detected at 2.33 eV photoionization energy parallels observations made previously 33 Although the IE a 's of BaNC and BaCN calculated in this work, of 5.19 and 5.28 eV, respectively, are higher than that of Ba(CH 3 CN) 1 (IE a = 4.12 eV; see Table II) or BaOH (IE a = 4.55 eV; Ref. 29), the intensity of the mass peak corresponding to BaNC+/BaCN+ is the highest upon photoionization at 2.3 eV [ Fig. 4(c)] due to the fact that this wavelength is resonant with an excited electronic state (C 2 Π-X 2 Σ + ; Ref.…”

“…The BaNC + (or BaCN + ) and BaOH + species are presumably products of the reaction in the cluster source between Ba + ions and molecules of acetonitrile and with impurities (mainly water), respectively. 29 These species then become solvated in acetonitrile clusters, most likely by the evaporative process: 25 The lower panel of Fig. 1 shows the relative populations of the Ba + (CH 3 CN) n and BaNC + (CH 3 CN) n families as a function of n, as derived from the integrated intensities of the mass peaks corresponding to their dominant barium 138 isotopic components.…”

Hydration of Barium Monohydroxide in (H2O)1–3 Clusters: Theory and Experiment

“…The experimental setup has been fully described in previous works. ,, Briefly, neutral BaOH(H 2 O) m clusters were generated in a pick-up source combining 1064 nm laser vaporization [(0.7–1.4) J cm –2 laser fluence] of a rotating Ba disk, with a supersonic expansion of a gaseous He:H 2 O (0.988: 0.012) mixture through a pulsed solenoid valve (400 μm diameter) at a stagnation pressure of 2 bar. The molecular beam of clusters was collimated with a 4.0 mm diameter skimmer placed 10 cm downstream from the nozzle, before entering into the ionization region of a differentially pumped Wiley–McLaren time-of-flight mass spectrometer (TOF-MS).…”

Photoionization and ab initio study of Ba(H2O)n (n = 1–4) clusters

“…The temperature of the species entrained in the molecular beam was previously estimated 48 to be in the range of 50-75 K, so a thermal correction on IE's of Ba(H 2 O) n clusters was not performed considering the uncertainty of the present determinations.…”